This invention relates to the enhancement of soft tissue wound repair by the application of weak electrostatic fields provided by one or more electret-type devices, and more particularly to a truly self-contained, yet wafer-thin, disposable bandage arrangement for application at the site of a soft tissue wound for enhancing the healing process. As used herein the word "wound" is intended to include: surgical incisions, abrasions, cuts, punctures, blemishes, tears, sores, blisters, burns, contusions, tissue ruptures and the like.
Over the last decade several reported studies have been conducted with the objective to demonstrate that the application of small electrical currents (in the micro ampere range) or weak magnetic or electrical fields would effect the growth or reunion of bone or enhance the repair of soft tissue (e.g. skin). While most of these have reported successes, it remains unclear even to the present time as to exactly why such applications have the effects that they do.
Representative of the successful techniques and systems for the repair of bone fracture or bone nonunion is the article of Z. B. Friedenberg et al, "Healing of Nonunion of the Metal Malleolus by Means of Direct Current: a Case Report", Journal of Trauma, 11, 883-885 (1971). Typically, a system representative of this work on bone structure is comprised of a special designed (constant) current circuit, usually battery powered, and containing two electrodes. The cathode is usually placed at one side of the fracture (situs), passing completely through the bone, and the anode on another portion of the bone or at a site distant from the fracture in or on the soft tissue. Application, of course, is via surgery. Customarily, the limb is then casted with the electronics strapped or taped to the cast.
From the work of Friedenberg, and others who have followed his general technique, an improved approach in the area of bone fracture repair has evolved which utilizes electromagnetic fields in a basically noninvasive technique. Such a technique is described, for example, in the article of C. A. L. Bassett et al., "Acceleration of fracture repair by electromagnetic fields. A surgically noninvasive method", Annals of the New York Academy of Science, 238, 242-262, 1974. In Bassett, for example, there is disclosed a system involving pulsed low frequency electromagnetic waves of low intensity being applied across a bone fracture site to induce voltages of a magnitude generally comparable to that produced by deformation (somewhat akin to piezoelectric response in bone distress). In this particular arrangement there is effected essentially a simulation of the natural piezoelectric generation of electricity in bone to accelerate the natural healing process in the bone. Such arrangements usually call for battery powered circuitry to provide the pulsed electromagnetic energy, which is applied to the situs through a pair of electrodes. In this improved technique, however, such electrodes usually take the form of relatively cumbersome plate-shaped electrodes placed on the skin overlying the bone to be treated.
The systems and techniques of the prior art as represented, for example, by Friedenberg and Bassett, are, of course, directed to bone structure as opposed to soft tissue. Such systems require for the most part, specially designed circuitry and associated electrodes which in at least some of the arrangements, are required to be surgically implanted. Such arrangements, moreover, require some form of power pack, usually employing batteries, which nevertheless, must be strapped or taped to the patient, and at the very least is bulky, clumsy and relatively heavy, and likely to impair the freedom of movement of the patient. Some of these prior art arrangements, further, require the generation of electric currents actually through the bone or the application of relatively high voltages (e.g. 24 volts), as to either or both of which patient safety may also be a factor. It may be generally said of such arrangements that there is required to be effected the active or dynamic generation or inducement of electrical currents or voltages in the body structure under treatment.
It is also known from U.S. Pat. No. 3,968,790 to Fukada et al. (The work of Fukada et al. is also found in Japan, J. Appl. Phys. Vol. 14, No. 12, [1975] "Callus Formation by Electret"), to surgically place in physical contact with or around a particular bone structure an electret type device for effecting callus formation and/or wound (i.e. fracture) repair. The Fukada work, however, is also limited to operation in connection with bone structure, utilizing an invasive technique for the application of an electret on or around the bone structure. It is, moreover, primarily concerned with callus formation on bone as opposed, for example, to the promotion of healing.
Another technique and apparatus for aiding formation of bone forming material is described in U.S. Pat. No. 3,745,995 to Kraus. The general technique covered therein involves invasive application of the disclosed structure on the bone itself. Intended is a splinting type arrangement involving partially noninvasively-applied structure. This latter-mentioned embodiment is rather bulky, however, being comprised of a pickup coil and a pair of electrodes straddling a region of the bone structure where callus formation is desired. Active field generation means are required for inducing in the pickup coil an AC current so as to induce alternating currents or potentials between the electrodes, which electrodes actually are embedded in the bone itself.
There have also been proposed systems and techniques aimed at treating soft tissue injuries, wherein the heating process is enhanced through the application of AC or DC currents right through and proximate the wound site. Such techniques are normally non-invasive and are represented, for example, by the work of D. Assimacopoulos, "Wound healing promotion by the use of negative electric current", American Surgeon, 34,423-431 (1968); L. E. Wolcott et al. "Accelerated healing of skin ulcers by electrotherapy: preliminary clinical results", Southern Medical Journal, 62,795-801 (1969); and J. J. Konikoff, "Electrical Promotion of Soft Tissue Repairs" Annals of Biomedical Engineering, 4,1-5, (1976). Common to such techniques in the direct application of a constant current output from an electronic circuit through an electrode attached to the site of lesion or repair and a second electrode, usually of the same material, located at a distance on or through the skin of the same organism. Such circuitry and devices are powered either by battery or through a converter from regular AC line current.
Such soft tissue-related techniques and systems possess many of the drawbacks of the bone structure-related systems and techniques, in that, for example, relatively, heavy clumsy and bulky supplies are required to provide the active generation of electrical current in and at the site of tissue repair. Also, electrodes are required to be attached or implanted to effect the path of current flow through the wound site. Moreover, while such arrangements, like those dealing with bone, tend to restrict the freedom of the patient, they are also generally undesirable from the standpoint of treating a patient on an out-patient basis or indeed in self-treatment instances.
In spite of the fact that the prior art makes use of electric fields to enhance bore fracture or directly applied electrical current to enhance and repair soft tissue, the prior art approach generally requires apparatus which is unwieldy or involves surgical invasive techniques. As such, ambulatory patients are indeed restricted during treatment; also, in many instances relatively minor wounds cannot be properly treated primarily because the patient is not confined to bed. Additionally, in those instances where batteries or battery packs are utilized, they must be replaced or recharged from time to time, which necessarily increases the total cost of treatment. Naturally, also, the potential for infection is ever present in those techniques and arrangements of the prior art requiring invasive surgery.
In addition to the need to overcome the drawbacks of the prior art, it would additionally be most desirable to provide a means and technique for soft tissue wound repair enhancement which allows for complete freedom of movement of the patient by means of a light-weight, wafer-thin, preferably self-adhering, self-contained, sterilized, disposable, statically-operable device, not having to be precisely fixed geometrically in relation to the wound site, and which may be shaped, tapered or cut relative to the wound area configuration itself.